Dock levelers are used at loading docks to bridge the gap between a loading dock and the bed of a vehicle parked at the loading dock to facilitate the loading or unloading of the vehicle. For example, dock levelers enable material handling equipment, such as a fork truck, to move between the dock and the vehicle bed.
Installation of dock levelers generally falls into two categories: pit-style dock levelers and edge-of-dock levelers. Pit-style dock levelers are installed in a pit or cavity below the level of the dock floor so that the top of the dock leveler is at dock level when stored. Pit-style dock levelers are typically configured to store horizontally, but some pit-style dock levelers store vertically. Examples of pit-style dock levelers are described in U.S. Pat. Nos. 3,368,229 and 4,928,340. Examples of vertical-storing dock levelers are found in U.S. Pat. Nos. 4,825,493 and 5,001,799. Pit-style dock levelers generally have the ability to service transport vehicles up to twelve inches above or below dock level. These dock levelers are typically activated by hydraulic, pneumatic, or mechanical spring systems. Pit-style dock levelers can be expensive to install due to the expense of the pit. Pit-style dock levelers, particularly horizontally-storing pit-style dock levelers, can also have the drawback of being more difficult to ensure security and environmental control.
Edge-of-dock levelers are attached to the dock wall and therefore do not require a pit or shelf for installation. Examples of edge-of-dock levelers can be found in U.S. Pat. Nos. 4,665,579 and 4,689,846. Edge-of-dock levelers are typically smaller and of simpler construction than pit-style dock levelers. A drawback of edge-of-dock levelers is that they can have limited range and below and steeper grades for fork trucks traveling over them.
A third type of dock installation that is known, but not widely used, is the horizontally-storing top-of-dock leveler. It is typically similar in construction to a horizontally-storing pit-style dock leveler but mounted on top of the dock without a pit. Top-of-dock levelers generally have limited below dock range and are generally used to service standard height trucks from a low dock. Also, top-of-dock levelers are generally used on an indoor dock, otherwise it requires that the door be modified to close properly.
Accordingly, it is desirable to provide a method and apparatus for bridging the gap between a dock and the end of a vehicle bed that can be installed economically such as with an edge-of-dock leveler, but which has greater vertical range and less steep grades than edge-of-dock levelers. It is also to desirable that the method and apparatus provide the security and environmental control of a vertically-storing dock leveler.